What is the difference between active transport and passive transport?

• A. Active transport occurs with energy and moves substances against their gradient
• B. Active transport occurs without energy while passive transport requires energy
• C. Active transport only occurs in plants, passive in animals
• D. Active transport is faster than passive transport at all times

Answer: (A)

Active transport is characterized by the use of energy, typically in the form of ATP, to move substances across a cell membrane against their concentration gradient. This means that active transport allows cells to accumulate substances internally at higher concentrations than are present outside the cell or to expel substances to the external environment in a regulated manner.

In contrast, passive transport does not require energy and involves the movement of substances down their concentration gradient, which means they move from areas of higher concentration to areas of lower concentration until equilibrium is reached. This passive movement occurs through mechanisms like diffusion and facilitated diffusion.

The correct answer highlights that active transport necessitates energy to move substances contrary to their natural tendency to diffuse away from areas of high concentration — an essential function for maintaining cellular homeostasis and proper physiological functions.